Why do SV's have engine braking?

... and in-line 4's don't?

Something to do with the inertia of 2 large capacity cylinders in a V configuration?

Sorry if this has been asked before. A girl (Flo) asked me, at the Skerries 100 road race, and I couldn't explain it

[BillyC]

Something to do with only 2 cylinders running in a 4 stroke pattern? The load has to spread over only 2 cylinders, instead of 4?

I'm only guessing - so this really isn't advice!

Originally Posted by Daz

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Something to do with the inertia of 2 large capacity cylinders in a V configuration?

It's something to do with that. I wouldnt know.

BUT my IL4 does have engine braking. Just not as much.


P.S. Change your Braking spelling before they have ya!

Originally Posted by mysteryjimbo

P.S. Change your Braking spelling before they have ya!

Cheers

I think it's something to do with crank case pressure. Bare with me here...

In an IL4 engine, imagine two of the cylinders going up while two go down. This means the volume of gas and therefore the pressure can stay the same.

Now look at the v-twin animation on the main site - the volume and pressure of gas in a v-twin crank case does not stay the same (which is why you need a breather pipe). So, when you roll off the throttle, the engine has to work against the constant varying crank case pressure, forcing gas in and out of the breather pipe.

I think thats why, I might be wrong though

Originally Posted by Flamin_Squirrel

IIn an IL4 engine, imagine two of the cylinders going up while two go down. This means the volume of gas and therefore the pressure can stay the same.

Now look at the v-twin animation on the main site - the volume and pressure of gas in a v-twin crank case does not stay the same (which is why you need a breather pipe). So, when you roll off the throttle, the engine has to work against the constant varying crank case pressure, forcing gas in and out of the breather pipe.

Erm........ but doesn't the breather pipe negate any pressure changes, thereby rendering your theory incorrect


I don't know what the answer to original theory is, but I suspect it's got more to do with pressures inside the cylinders than inside the crankcase.

Originally Posted by Jabba-the-Hutt

Erm........ but doesn't the breather pipe negate any pressure changes, thereby rendering your theory incorrect


I don't know what the answer to original theory is, but I suspect it's got more to do with pressures inside the cylinders than inside the crankcase.

It allows the pressure to equalise, but the engine would still have to work against it. But as I say, I'm not sure if that's the actual reason.

embee!?

[ophic]

this is something that has intrigued me for a while too. Engine braking, btw, is caused by a number of factors including drive train friction. But the part that varies between motors is the effect of the piston head pulling against a closed throttle. Or so I've read.

I can't say why the engine configuration should make any difference. The only thing that seems to make a difference is the cylinder characteristics. Twins tend to have bigger cylinders with longer strokes. Hence they create more of a vacuum when pulling against a closed throttle. But that still doesn't make sense because a Hayabusa's cylinders are more or less the same size and shape as an SV.

Compression ratio would also have a marked effect, only in the case of engine braking its really expansion ratio. Again the 'busa is pretty much the same as the SV.

So i think i've basically said... I don't know

just tell the girl u dont know and say to her if she wants to go for a spin with you she can see for herself . cos it seems to me it was just a chat up line and you missed your chance lol

Originally Posted by pip

just tell the girl u dont know and say to her if she wants to go for a spin with you she can see for herself . cos it seems to me it was just a chat up line and you missed your chance lol

... she's married and has a 636. It's was an interesting question though. I was telling her watch for my bike slowing and not to run into the back of me.